1. Field of the Invention
The present invention relates to a liquid jet head for discharging a desired liquid by causing thermal energy to act upon liquid for the creation of air bubbles, a head cartridge using such liquid jet head, a liquid jet apparatus, a method for manufacturing liquid jet heads, a liquid discharging method, a recording method, and recorded objects obtained by utilizing such liquid discharging method.
More particularly, the present invention relates to a liquid jet head provided with movable members displaceable by the utilization of the creation of air bubbles, a head cartridge using such liquid jet head, and a liquid jet apparatus or the invention relates to a liquid discharging method for discharging liquid by displacing. movable members by the utilization of the creation of air bubbles, and a recording method.
The present invention is also applicable to a printer for recording on a recording medium, such as paper, thread, fabric, cloth, leather, plastic, glass, wood, or ceramics, and to a copying machine, a facsimile equipment provided with communication systems, a word processor and other apparatuses having a printing unit therefor. Further, the present invention is applicable to a recording system for industrial use, which is complexly combined with various processing apparatuses.
Here, the term xe2x80x9crecordingxe2x80x9d in the description of the present invention means not only the provision of images having characters, graphics, or other meaningful representation, but also, the provision of those images that do not present any particular meaning, such as patterns.
2. Related Background Art
There has been known the so-called bubble jet recording method, which is an ink jet recording method whereby to form images on a recording medium by discharging ink from discharge ports using acting force exerted by the change of states of ink brought about by the abrupt voluminal changes (creation of air bubbles) when thermal energy or the like is applied to ink in accordance with recording signals. For the recording apparatus that uses the bubble jet recording method, it is generally practiced to provide, as disclosed in the specifications of U.S. Pat. No. 4,723,129 and others, the discharge ports that discharge ink, the ink paths conductively connected to the discharge ports, and electrothermal transducing elements arranged in each of the ink paths as means for generating energy for discharging ink.
In accordance with such recording method, it is possible to record high quality images at high speeds with a lesser amount of noises. At the same time, the head that executes this recording method makes it possible to arrange the discharge ports for discharging ink in high density, with the excellent advantage, among many others, that images are made recordable in high resolution, and that color images are easily obtainable by use of a smaller apparatus. In recent years, therefore, the bubble jet recording method is widely adopted for many kinds of office equipment, such as a printer, a copying machine, a facsimile equipment. Further, this recording method is utilized even for industrial systems, such as a textile printing, among others.
Along the wider utilization of bubble jet technologies and techniques for various products in many different fields, there have been increasingly more demands in recent years as given below.
For example, as to the demand on the improvement of discharging efficiency, the adjustment of the thickness of protection film has been studied to optimize the performance of heat generating elements. A study of the kind has produced effects on the enhancement of transfer efficiency of generated heat to liquids.
Also, in order to obtain high quality images, there has been proposed a driving condition under which a liquid discharging method or the like is arranged to be able to execute good ink discharges at higher ink discharging speeds with more stabilized creation of air bubbles. Also, from the viewpoint of a high-speed recording, there has been proposed the improved configuration of liquid flow paths that makes it possible to obtain a liquid jet head capable of refilling liquid to the liquid flow paths at higher speeds in order to make up the liquid that has been discharged.
Of the various configurations of liquid flow paths thus proposed, the structure of liquid flow paths is disclosed in the specification of Japanese Patent Application Laid-Open No. 63-199972 as shown in FIGS. 47A and 47B. The structure of the liquid flow paths and the method for manufacturing disclosed in the specification thereof are the inventions devised with attention given to the back waves (the pressure directed opposite to the direction toward the discharge ports, that is, pressure exerted in the direction toward the liquid chamber). The back waves are known as energy loss because such energy is not exerted in the discharging direction.
The invention represented in FIGS. 47A and 47B discloses a valve 55, which is arranged away from the air bubble generating area formed by the heat generating element 2, and which is positioned on the side opposite to the discharge port 18 with respect to the heat generating element 2.
As shown in FIG. 47B, this valve 55 is set at the initial position thereof such as adhesively bonded to the ceiling of the liquid flow path 10 by method of manufacture utilizing a plate material or the like. In the disclosure, the valve is described as such to be caused to hang down in the liquid flow path 10 along the creation of air bubble. It is also referred to in the disclosure that the invention is designed to control the aforesaid back waves partly by the provision of the valve 55 in order to suppress the energy loss.
However, with respect to the structure thus disclosed, it is clearly understandable that the partial suppression of the back waves by means of the valve 55 is not practical for liquid discharge when studies are made on the condition under which the air bubbles are created in the liquid flow path that retains the discharging liquid in it.
Fundamentally, the back waves themselves are not related directly with discharging as described above. Of the pressures exerted by the air bubble, those directly related with discharging have already acted upon liquid so that the liquid is in the state of being discharged from the liquid flow path the moment the back waves are generated in the flow path as shown in FIG. 47B. Therefore, even if the back waves are suppressed, it is clear that no significant influence is exerted on the liquid discharge, not to mention the partial suppression of the back waves.
Also, in the specification of Japanese Patent Application Laid-Open No. 63-199972, an invention of the head is disclosed. This head is made excellent in the frequency response by improving the refilling of recording liquid. In accordance with such invention, a sub-flow path is arranged, and this path is connected with the corresponding nozzle in the vicinity of the heater. At the time of refilling, ink is also supplied from this sub-flow path, thus attempting to make the refilling period shorter.
However, with the head thus structured, part of the discharging power generated at the time of bubble generation escapes to the sub-flow path, and there is a fear that the discharging efficiency is lowered inevitably. On the other hand, for the bubble jet recording method, each of the heat generating elements repeats heating, while being in contact with ink. As a result, deposit is accumulated on the surface of each heat generating element due to burning of ink. Depending on the kinds of ink, such deposit is made in a considerable quantity, and results in the instabilized creation of air bubbles, hence making it difficult to perform ink discharges in good condition. Also, it is desired to provide a method for performing discharges in good condition without changing the quality of discharging liquid even when the liquid used has the nature such as to be easily deteriorated by the heat application or such as to make sufficient bubble generation difficult.
Here, with this in view, there has been proposed a method for discharging liquid by transferring pressure exerted by bubble generation to discharging liquid, while arranging means for separating the liquid used to create air bubbles by the application of head (bubbling liquid) and the liquid for use of discharges (discharging liquid) as different liquids, such as disclosed in the specifications of Japanese Patent Application Laid-Open No. 61-69467, Japanese Patent Application Laid-Open No. 55-81172, U.S. Pat. No. 4,480,259, among some others. In accordance with these disclosures, the structure is arranged to completely separate ink serving as discharging liquid, and bubbling liquid by use of silicon rubber or some other flexible film so as not to allow the discharging liquid to be directly in contact with the heat generating elements, and at the same time, to transfer pressure exerted by foaming of the bubbling liquid to the discharging liquid by means of the deformation of the flexible film. With a structure of the kind, it is attained to prevent the deposit from being accumulated on the surface of each heat generating element, the improvement of selection range of discharging liquids, or the like.
However, the structure that completely separates discharging liquid and bubbling liquid as described above is the one whereby to transfer pressure exerted at the time of bubble generation to discharging liquid by means of the deformation of the flexible film brought about by its expansion and contraction. Therefore, the pressure exerted by the deforming thereof is absorbed by the flexible film to a considerable extent. Also, the amount of deformation of the flexible film is not large. As a result, although it is possible to obtain effect that discharging liquid and bubbling liquid are made separable, there is a fear that discharging efficiency and discharging power are lowered after all.
The subject of the present invention is to enhance the fundamental discharging characteristics of the conventional method for discharging liquid by the creation of air bubbles (particularly, air bubbles following film boiling) in each of the liquid flow paths to such a high level that has never been anticipated conventionally from the viewpoint that has not been given any light in the conventional art.
Some of the inventors hereof have returned to the principle of liquid droplet discharging, and carried out researches and developments assiduously on a new method for discharging liquid droplets by the utilization of air bubbles, which has never been attempted, as well as on the provision of a head and others usable for such method. At that time, it has been executed to make a first technical analysis of the principle of mechanism of the movable member in the flow path, starting with the operation of the movable member in the liquid flow path; a second technical analysis based upon the principle of the liquid droplet discharging by means of air bubbles; and a third technical analysis based upon the air bubble generating area of each heat generating element for use of the air bubble creation.
These technical analyses have led to the establishment of a completely new technique that the air bubbles are positively controlled by arranging a positional relationship between the fulcrum and free end of the movable member so that the free end thereof is positioned on the discharge port side effectively, namely, on the downstream side, and also, positively controlled by arranging the movable member to face the heat generating element of the air bubble generating area appropriately.
Then, it has been known that in consideration of the energy that each air bubble itself gives to the discharge amount, the greatest factor that contributes to the significant enhancement of the discharging characteristics is the developing component of the air bubble on the downstream side, and that attention should be given to this developing component. In other words, it is the prerequisite for the enhancement of the discharging efficiency and discharging speed that the developing component of the air bubble on the downstream side is converted efficiently to be the one directed toward discharging. Based on such knowledge thus obtained, some of the inventors hereof have acquired a technique of an extremely high standard as compared with the conventional technical standard that the developing component of the air bubble on the downstream side is allowed to shift to the free end side of the movable member positively.
Further, it has been found preferable to consider the heat generating area for the creation of air bubbles, which is on the downstream side of the center line that passes the area center of each electrothermal transducing element in the flow direction of liquid, for example, or to consider the structural elements of the movable member with respect to the development of each air bubble on the downstream side of the area center in order to promote foaming or the like.
In accordance with the knowledge obtained by the researches and developments described above, and also, from the overall point of view, some of the inventors hereof and the present applicant have already filed an application for a patent on an excellent principle of liquid discharging. The inventor et al. hereof have acquired a more preferable concept on the premise of such invention.
In other words, with respect to the structure that enable the movable member to face the air bubble generating area, there are some cases where slight variation takes place depending on the conditions of design set for remarkably enhancing the discharging characteristics and discharging stability as compared with the conventional structure where no movable member is provided. It has been found that the important factor for the discharging condition to be brought to a higher level is the state in which the movable member leads air bubble in the direction of discharge port, that is, how fast the movable member is brought to the ideal configuration of its displacement.
Based upon this finding, the applicant hereof has applied for a patent by Japanese Patent Application No. 8-40553, which is intended to provide a changing point with respect to the thickness of the movable member itself for the quick displacement of the movable member as given below.
xe2x80x9cA liquid jet head for discharging liquid by the creation of air bubbles, comprising the discharge ports for discharging liquid, liquid flow paths conductively connected with the discharge ports, air bubble generating areas for causing liquid to create air bubbles, and movable members arranged on the air bubble generating areas, each having the fulcrum point and the free end positioned relatively on the discharge port side with respect to the fulcrum point,
the movable member having a curbed portion for changing the relative displacements of the movable portion on the free end side and the movable portion of the fulcrum side.xe2x80x9d
On the related background art described above, the present invention is designed for the quick and reliable movement of the free end of the movable member displaceable by the creation of air bubble, and also, for the provision of a method of solution devised differently from the previous invention in which attention is given only to the movable member itself.
In other words, the principle objective of the present invention is as follows:
It is a first object of the invention to provide a method for promoting displacement and means therefor with respect to the movable member, except for the thickness changes of the movable member on the free end side, by giving attention to the load conditions or the structural relations for promoting the movement of the free end of the movable member.
It is a second object of the invention to provide a liquid discharging method and a liquid jet head whereby to attain the quicker displacement of the free end of the movable member at the early stage of the air bubble creation, thus obtaining a state where the air bubble is led to the discharge port in a shorter period of time.
It is a third object of the invention to provide a liquid discharging method and a head using such method in order to enhance the durability of the movable member.
It is a fourth object of the invention to provide a liquid jet head capable of making the time required for the maximum displacement of the free end of the movable member shorter in order to enhance the printing speeds.
It is a fifth object of the invention to provide a liquid jet head capable of reducing the deformation of the movable member brought about by the resistance taking place in the liquid flow path when the valve mechanism of the movable member operates by the creation of air bubble, thus enhancing the discharging efficiency of the head.
It is a sixth object of the invention to provide a liquid jet head capable of suppressing more quickly the inertial force acting in the direction opposite to the direction of liquid supply due to the generation of back waves, and at the same time, capable of making the printing speeds higher by reducing the regressive amount of meniscus by use of the valve mechanism of the movable member to enhance the refilling frequency.
It is a seventh object of the invention to provide a liquid jet head and a liquid discharging method capable of leading air bubble in the discharging direction by bringing the discharging configuration of the movable member to its ideal status by means of the characteristics provided for the movable member, thus enhancing the discharging efficiency and discharging stability.
It is an eighth object of the invention to provide a liquid jet head and a liquid discharging method whereby to materialize the structure of the movable member capable of utilizing the function to positively shift the developing component of the air bubble on the downstream side to the free end side of the movable member, hence attempting the further enhancement of discharging efficiency and discharging pressure for the implementation of more stable liquid discharging.
It is a ninth object of the invention to provide a head cartridge and a liquid jet apparatus using the liquid jet head of the present invention.
In order to solve the problems described above, the present invention provides means for intensively arranging the air bubble generating area on the free end side of the movable member given below with the exception of the thickness changes of the free end side of the movable member; means for making the characteristic frequency of vibration of the movable member larger than the driving frequency (preferably, the maximum driving frequency) for use of air bubble creation, and means for promoting displacement to promote the movement of the free end of the movable member.
(a) Means for intensively arranging the air bubble generating area on the free end side of the movable member.
(1) For a liquid jet head for discharging liquid by displacing the movable member provided with the free end facing the air bubble generating area by means of air bubble, the pressure of air bubble is added to the xc2xd area from the free end side of the movable member or preferably, ⅖ area from the free end side thereof, thus enabling the displacement of the free end to be in the displacing configuration that makes it maximum.
(2) For a liquid jet head for discharging liquid by displacing the movable member provided with the free end facing the air bubble generating area by means of air bubble, the pressure of the air bubble acting upon the side nearer to the free end of the movable member is enhanced relatively more than the pressure acting upon the side nearer to the fulcrum in order to make the displacement of the free end higher than any other parts of the movable member.
(b) Means for making the characteristic frequency of vibration of the movable member larger than the driving frequency for use of air bubble creation, and means for promoting displacement
(3) For a liquid jet head for discharging liquid by displacing the movable member provided with the free end facing the air bubble generating area by means of air bubble, the characteristic frequency of vibration of the movable member is made larger than the inverse number of cycle from the creation of air bubble to the extinction thereof.
(c) Means for promoting displacement to promote the movement of the free end of the movable member
(4) For a liquid jet head for discharging liquid by displacing the movable member provided with the free end facing the air bubble generating area by means of air bubble, the free end side of the movable member is arranged to be a first displacement area, and the fulcrum side is arranged to be a second displacement area having a stronger rigidity that the first displacement area in the displacing direction of the movable member, and the developing component of the air bubble on the downstream side is positively shifted to the free end side of the movable member.
(Modes Embodying the Present Invention)
Now, the description will be made of the modes embodying the present invention.
In accordance with the present invention, a liquid discharging method for discharging liquid by displacing a movable member having the free end thereof facing an air bubble generating area by means of air bubble comprises the step of promoting the movement of the free end by means for promoting the displacement of the free end of the movable member.
In accordance with the present invention, a liquid jet head for discharging liquid by displacing a movable member having the free end thereof facing an air bubble generating area by means of air bubble comprises means for promoting displacement to promote the displacement of the free end of the movable member.
In accordance with the present invention, means for promoting displacement of the present invention includes means for intensively arranging the air bubble generating on the free end side of the movable member with the exception of the thickness changes of the free end side of the movable member; means for making the characteristic frequency of vibration of the movable member larger than the driving frequency (preferably, the maximum driving frequency) for use of air bubble creation; means for promoting the movement of the free end of the movable member, or the like.
(a) Means for intensively arranging the air bubble generating area on the free end side of the movable member.
In accordance with the present invention, a liquid discharging method is to add the pressure of air bubble to a xc2xd area from the free end side of the movable member for the provision of a displacing configuration to maximize the displacement of the free end.
In accordance with the present invention, a liquid discharging method is to add the pressure of air bubble to a ⅖ area from the free end side of the movable member for the provision of a displacing configuration to maximize the displacement of the free end.
In accordance with the present invention, a liquid jet head is structured to arrange the end of the air bubble generating area on the side opposite to the discharge port on the free end side of the center of the movable member.
In accordance with the present invention, a liquid jet head is to arrange the air bubble generating area on the side opposite to the discharge port on the free end side of the point dividing the movable member by 2:3 from the free end thereof.
In accordance with the present invention, a liquid discharging method is to enhance the pressure of the air bubble acting upon the side nearer to the free end relatively more than the pressure acting upon the side nearer to the fulcrum, among pressures acting upon the movable member, in order to make the displacement of the free end higher than any other parts of the movable member.
In accordance with the present invention, a liquid discharging method uses a head provided with discharge ports for discharging liquid, air bubble generating areas for causing liquid to create air bubbles, and movable members arranged to face the air bubble generating areas, each being displaceable between a first position and a second position further away from the air bubble generating area than the first position,
this movable member being displaced from the first position to the second position by pressure exerted by the creation of air bubble on the air bubble generating area, at the same time, the air bubble being caused to be expanded by the displacement of the movable member larger on the downstream than on the upstream in the direction toward the discharge port for discharging liquid, and then, the pressure of the air bubble acting upon the side nearer to the free end being enhanced relatively more than the pressure acting upon the side nearer to the fulcrum, among pressures of the air bubble acting upon the movable member, in order to make the displacement of the free end higher than any other parts of the movable member.
In accordance with the present invention, a liquid jet head is to enhance the pressure of air bubble acting upon the movable member on the side nearer to the free end side more than the pressure acting upon the side nearer to the fulcrum side, among pressures of the air bubble acting upon the movable member, in order to make the displacement of the free end higher than any other part of the movable member.
In accordance with the present invention, a liquid jet head is provided with discharge ports for discharging liquid, air bubble generating areas for causing liquid to create air bubbles, and movable members arranged to face the air bubble generating areas, each being displaceable between a first position and a second position further away from the air bubble generating area than the first position, and
this movable member being displaced from the first position to the second position by pressure exerted by the creation of air bubble on the air bubble generating area, at the same time, the air bubble being caused to be expanded by the displacement of the movable member larger on the downstream than on the upstream in the direction toward the discharge port for discharging liquid, and then, the pressure acting upon the side nearer to the free end is enhanced relatively more than the pressure acting upon the side nearer to the fulcrum, among pressures acting upon the movable member, in order to make the displacement of the free end higher than any other parts of the movable member.
(b) Means for making the characteristic frequency of vibration of the movable member larger than the driving frequency for use of air bubble creation.
In accordance with the present invention, a liquid jet head is to make the characteristic frequency of vibration of the movable member larger than the inverse number of cycle from the creation of air bubble to the extinction thereof.
In accordance with the present invention, a liquid jet head is to make the speed of wave transfer of the movable member faster than the developing speed of air bubble.
In accordance with the present invention, a liquid discharging method is to use such liquid jet head described above.
(c) Means for promoting displacement to promote the movement of the free end of the movable member.
In accordance with the present invention, a liquid jet head comprises discharge ports for discharging liquid, air bubble generating areas for creating air bubbles for discharging liquid from the discharge ports, and at least one movable member arranged to face the air bubble generating area to be made displaceable between a first position and a second position further away from the air bubble generating area than the first position,
this movable member being provided with the fulcrum on the upstream side, and the free end on the downstream side in the flow of liquid directed to the discharge port, and provided with a first displacement area on the free end side, and a second displacement area on the fulcrum side, having stronger rigidity than the first displacement area with respect to the displacing direction of the movable member, and being displaced from the first position to the second position by pressure exerted by the creation of air bubble to lead the pressure in the direction of the discharge port for discharging liquid from the discharge port.
In accordance with the present invention, a liquid discharging method comprises the step of arranging movable members, each having the fulcrum on the upstream side and the free end on the downstream side in the flow of liquid directed toward the discharge port, and a first displacement area on the free end side and a second displacement area on the fulcrum side provided with a stronger rigidity than the first displacement area with respect to the displacing direction, to face the air bubble generating area for creating the air bubble; and the step of leading pressure in the direction of the discharge port for discharging liquid from the discharge port by displacing the movable member from a first position to a second position further away from the air bubble generating area than the first position by the pressure exerted by the creation of air bubble on the air bubble generating area for discharging liquid from the discharge port.
In accordance with the present invention, a head cartridge is provided with the liquid jet head described above, and a liquid container for retaining liquid to be supplied to the liquid jet head.
Also, in accordance with the present invention, a liquid jet apparatus is provided with the liquid jet head described above, and a carriage mounting the liquid jet head, and being capable of reciprocating in the sub-operational direction for recording on a recording medium.
In this respect, the terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are related with the direction of liquid flow from the supply source of liquid to the discharge port through the air bubble generating area (or the movable member) or these terms are often used to express the structural direction thereof.
Also, the term xe2x80x9cdownstream sidexe2x80x9d of the air bubble itself represents the portion of the air bubble on the discharge port side, which mainly acts upon the discharge droplets directly. More specifically, it means the downstream side with respect to the center of the air bubble in the flow direction or the structural direction described above or the air bubble created in the area on the downstream side of the area center of the heat generating element.
Also, the term xe2x80x9cessentially closedxe2x80x9d used in the description of the present invention means a state where the air bubble does not escape from the gap (slit) on the circumference of the movable member before the movable member is displaced at the time of the air bubble being developed.
Also, the term xe2x80x9cseparation wallxe2x80x9d referred to in the present invention means a wall (that may include the movable member) that resides to partition the air bubble generating area and the discharge port in a broader way, and also, means the partition between the flow path including the air bubble generating area and the liquid flow path conductively connected with the discharge port directly, in a narrower way, so as to prevent liquid in each of the areas from being mixed.
Also, the term xe2x80x9cthe pressure of air bubble caused to act upon the movable memberxe2x80x9d referred to in the description of the present invention includes at least either one of the pressure wave propagated from the air bubble to the movable member along the creation of air bubble and the development thereof, and the force that acts upon the movable member, which is exerted by the shifting of liquid residing between the air bubble and the movable member following the pressure of air bubble.
Also, the term xe2x80x9cthe center of the movable memberxe2x80x9d referred to in the description of the present invention means the portion of the movable member intersecting the vertical surface that bisects the length from the free end to the fulcrum of the movable member with respect to the upstream and downstream directions of ink flow.